Conventionally, a semiconductor chip having a semiconductor element such as an IGBT is packaged together with a metal block and/or a heat radiation plate so that a package semiconductor equipment is formed. This equipment is described in, for example, Japanese Patent No. 3750680 (corresponding to U.S. Pat. No. 7,009,292). In the equipment, an emitter aluminum electrode is formed on a surface of a semiconductor substrate, on which the IGBT is formed. Further, a gate wiring layer is formed on the surface of the substrate through a LOCOS oxide film and an insulation film.
To isolate the emitter aluminum electrode from the gate wiring layer so as not to short-circuit, a protection film is formed to cover the surface of the gate wiring layer. The emitter aluminum electrode and the gate wiring layer are electrically insulated from each other with the protection film. A metal block is bonded to the emitter aluminum electrode and the protection film via a solder layer.
However, in the above conventional art, when disturbance is applied to the equipment, the protection film may be cracked. In this case, the solder layer may penetrate into the crack to reach the gate wiring layer, so that the emitter aluminum electrode and the gate wiring layer may short-circuit.
The factor of generation of the crack in the protection film is not only the disturbance but also process failure, which occurs in a step for forming the protection film. For example, in JP-A-2007-27565, after the protection film and a metal film are formed on a semiconductor substrate, a part of the metal film on the protection film is removed by cutting a part of the protection film and the metal film with a bit for cutting. The part of the metal film is an unnecessary part.
Since the bit cuts the protection film under the metal film, the protection film may be damaged. Thus, a crack may be generated in the protection film. Similar to the disturbance, the solder layer may penetrate into the crack to reach the gate wiring layer, so that the emitter aluminum electrode and the gate wiring layer may short-circuit.
Thus, when the protection film is formed or after the protection film is formed, the crack may be generated in the protection film. Thus, if the solder layer penetrates through the crack and reaches the gate wiring layer, the emitter aluminum electrode and the gate wiring layer may short-circuit.